Zinc-Coated Steel Strand for Messenger Support of Figure 8 Cable

A640-97 (Reapproved 2014): Standard Specification for Zinc-Coated Steel Strand for Messenger Support of Figure 8 Cable

When designing and deploying critical communication and electrical infrastructure, the reliability and longevity of supporting components are paramount. For professionals engaged in the construction of Figure 8 cables, understanding the specifications for their integral messenger support is essential. ASTM's A640-97 (Reapproved 2014) standard provides an authoritative framework for the zinc-coated steel strand used in these demanding applications, ensuring structural integrity and protection against environmental degradation.

What is A640-97 (Reapproved 2014)?

ASTM A640-97 (Reapproved 2014) is an industry-leading standard that meticulously defines the requirements for extra-high-strength grade, zinc-coated steel wire strand specifically engineered for use as the supporting messenger in Figure 8-type communication and electrical cables. Originating from ASTM's commitment to material standards, its primary purpose is to ensure a consistent, high-quality product that can reliably bear the load and withstand environmental challenges inherent in overhead cable deployments.

Scope & Purpose

This comprehensive standard governs the materials, manufacturing processes, and physical properties of zinc-coated steel strand intended for messenger support in Figure 8 cable constructions. It specifies the composition of the steel wire, the zinc coating requirements, stranding methods, and acceptable joint types. The standard explicitly addresses the application of sealing compounds to prevent moisture ingress, a critical factor for cable longevity. However, it does not cover the plastic sheathing of the cable itself or the final cable assembly beyond the messenger strand.

Who Must Comply?

• • Primary audience: Materials Engineers, Cable Design Engineers, Quality Control Inspectors, Production Supervisors, and Procurement Specialists involved in the telecommunications and electrical utility sectors.
• • Industries affected: Telecommunications, Electrical Power Transmission and Distribution, and Cable Manufacturing.
• • Compliance nature: Voluntary, but adoption is highly recommended by end-users and specifiers to ensure proven performance and product quality.
• • Enforcement: Typically enforced through contractual agreements, project specifications, and quality assurance programs implemented by cable manufacturers and their clients.

Key Requirements Overview

Professionals must ensure that the zinc-coated steel strand procured or manufactured adheres to the following core provisions:

• • The standard requires stringent control over the steel base metal composition and the drawing process for individual wires to achieve uniform quality.
• • Key provisions include specific requirements for the weight and adherence of the zinc coating to ensure robust corrosion resistance.
• • Manufacturers must ensure that the strand is constructed with a uniform lay and pitch, and that individual wires lie naturally without significant distortion.
• • The specification details acceptable methods for joining individual wires, emphasizing that such joints must be well-made and provide equivalent corrosion protection to the base wire.
• • Stringent mechanical properties, including minimum breaking strength and elongation, are mandated to guarantee performance under load.

Related Standards & References

ASTM A640-97 (Reapproved 2014) works in conjunction with other ASTM standards to provide a complete material specification. Complementary standards include:

• • ASTM A90/A90M: Test Method for Weight [Mass] of Coating on Iron and Steel Articles